DEGRADABILITY OF FORAGE PROTEIN SUPPLEMENTS AND THEIR EFFECTS ON THE KINETICS OF DIGESTION AND PASSAGE

Degradability characteristics of oats hay (harvested at milk stage), o ats straw, wheat middlings and forage legumes (lablab (Lablab purpureu s) hay, leaves of sesbania (Sesbania sesban) and tagasaste (Chamaecyti sus palmensis)) were evaluated in three sheep given native hay supplem ented with cottonseed cake. In Trial 2, 18 fistulated male sheep were given six dietary treatments: ad libitum oats straw with 250 g (as fed ) of lablab hay; ad libitum oats hay alone or supplemented with either 250 g (as fed) of lablab hay, wheat middlings (WM), sesbania or tagas aste. The effect of these diets on degradabilities of oats hay and oat s straw and rumen particulate passage rate (k1) were determined. Oats hay had higher (P < 0.05) solubility, potential dry matter (DM) degrad ability and soluble nitrogen (N) (631 vs. 498 g per kg; P < 0.01) than oats straw. Oats hay DM degraded 2.3 times faster than oats straw whe n both were supplemented with lablab. Sheep given hay-lablab diet had a faster k1 (0.0371 vs. 0.0173 h(-1); P < 0.01) and consumed more roug hage (606 vs. 447 g per day; P < 0.01) than those given straw-lablab d iet. Sesbania had the highest potential DM degradability (921 g per kg ) followed by WM (846), tagasaste (762) and lablab (706). WM (DM) degr aded fastest followed in order by sesbania, lablab and tagasaste. Labl ab had the highest soluble N (737 g per kg) and differed (P < 0.001) f rom sesbania (298), WM (526) and tagasaste, which was negative (-38). Sesbania had the highest potential N degradability (922), followed by lablab (846), WM (849) and tagasaste (737). Supplements had similar (P > 0.05) N degradation rates. Supplementation and type of supplement h ad no effect on any of the degradation characteristics of oats hay. Sh eep given WM had the fastest k1 followed in order by lablab, sesbania and tagasaste. Supplementation increased the intakes of DM (P < 0.01) and N (P < 0.05) but not of neutral detergent fibre (NDF); but supplem ent types had no effect (P > 0.05) on the intake of oats hay, total DM or NDF. It was concluded that supplementation with forage legumes had no effect on oats hay DM degradation rate but tended to enhance k1. F orage legumes that disappear fast from the rumen may induce lower subs titution rates.